This site contains a huge number of lessons, complete with texts, vocabulary, audio, exercises and much more. And it's all free. Note that if you want to get the intermediate and advanced material,... Read more.

collections.uiowa.edu

Word Reference offers several good forums for discussing languages and this is the Chinese section. It's perhaps not as active as Chinese Forums and I don't follow this forum regularly, so I don't... Read more.

forum.wordreference.com

Langademy is a language learning social network that connects students with natives from all over the world. Students can practice Chinese, English, French or any other language at Langademy by mak... Read more.

langademy.com

This page offers several hundred lessons for Chinese about different topics, including both reading practice and listening. They also have some learning activities, including quizzes. I have tried ... Read more.

gloss.dliflc.edu

Forumosa is a major online forum where you can discuss anything regarding Taiwan, including living there, learning Chinese, finding friends, jobs or language exchange partners and much more. There'... Read more.

forumosa.com

From their website (if you have personal experience of their courses, please leave a comment): New Concept Mandarin specializes in teaching Mandarin Chinese (Putonghua) as a second language. Act... Read more.

newconceptmandarin.com